1. Technical Field
The present invention relates to a light control device mounted on a vehicle, particularly to a device that controls lighting of the light based on illuminance around the vehicle.
2. Related Art
Conventionally, there is well known automatic light control in which a sensor detects the illuminance around the vehicle to automatically turn on and off a headlight of the vehicle. For example, Japanese Unexamined Patent Publications Nos. 2008-80932, 2001-163115, and 2007-302046 disclose the automatic light control.
In Japanese Unexamined Patent Publication No. 2008-80932, an ultraviolet sensor, an infrared sensor, and a visible-light sensor are provided in order to surely distinguish artificial light and natural light from each other to precisely perform the light control. In Japanese Unexamined Patent Publication No. 2001-163115, whether surroundings of the vehicle become gloomy at dusk is determined based on a comparison result of the illuminance detected by an illuminance sensor and a threshold, and a time change of the illuminance. In Japanese Unexamined Patent Publication No. 2007-302046, an iris of a driver is detected by an eye camera to change a lighting threshold at twilight gloom.
The illuminance around the vehicle changes depending on time periods such as morning, daytime, evening, and night, and the illuminance also changes when the vehicle goes in dark places such as in a tunnel, under an elevated structure, and in a shadow of a building. Therefore, in the automatic light control, it is necessary to accurately detect the illuminance around the vehicle, which changes depending on the environment. Particularly, at the dusk in which the surroundings of the vehicle become gloomy, a risk of an accident generation increases when the lighting is delayed. Accordingly, from the viewpoint of accident prevention, it is necessary that the automatic light control be performed such that the light is turned on in precise timing.